The Supreme Leader of Iran, Ayatollah Seyed Ali Khamenei, issued a vague warning to the U.S. government Sunday, which he called the "most malicious Satan," saying any "wrong move" with regard to the 2015 nuclear deal will spark a "reaction."

"In this connection [to the nuclear deal], they show a mischief and satanic gesture each day, showing the right statement of the great Imam [the late Ayatollah Ruhollah Khomeini] that the U.S. is a big Satan and actually the U.S. is the most malicious Satan," Khamenei said, according to an English translation from Iran's official Islamic Republic News Agency. (Khomeini, Khamenei's predecessor, often referred to the U.S. as the "Great Satan," even in his will.)

"Officials should prove to the corrupt rulers of the U.S. that they rely on their people and Iranian nation is a great nation and under blessing of Islam they will not succumb to pressure and will not bow to them," Khamenei reportedly went on. "[The] enemy should know that if bullying proves effective in other parts of the world, it will not be so in the Islamic Republic and the system is authoritative and strong."

Khamenei's comments came as he spoke at a graduation ceremony for police cadets, according to Iran's English-language Fars news service.

The 2015 nuclear deal, officially the Joint Comprehensive Plan of Action (JCPOA), has come under renewed scrutiny ahead of U.S. President Donald Trump's first ever address to the United Nations General Assembly Tuesday. Trump is reportedly expected to discuss the Obama-era deal, which he has previously called the "worst deal ever" and one with which Iran is not fully complying. (Trump also said in 2015 he will never refer to Khamenei as "Supreme Leader," but joked he might start a conversation with him about JCPOA with, "Hey you... how, you doin' babe?")

"We are not going to stand for what they're doing to this country," Trump told reporters Thursday, according to The New York Times. "They have violated so many different elements, but they've also violated the spirit of that deal. And you will see what we'll be doing in October. It will be very evident."

By mentioning October, Trump is presumably referencing the next time his administration will be compelled to declare to Congress whether Iran is in violation of the deal, a requirement every 90 days. The last time the Trump administration had to do so was in July, which it did, but reportedly unhappily. Last week the administration declined to re-instate sanctions against Iran that were waived as part of the deal, preserving the status quo for now.

In broad strokes, in the JCPOA Iran agreed to a number of measures, including independent inspections, meant to satisfy the international community that it would not pursue nuclear weapons in the near term. In return, the U.S., the European Union and the United Nations agreed to lift some economic sanctions on Iran, and the U.S. unfroze Iranian financial assets measuring in the tens of billions of dollars (PDF).

The latest report (PDF) from the International Atomic Energy Agency, a U.N. body charged with inspecting Iran's nuclear facilities, says Iran appears to be in compliance with the accord, as of the report's August 31 dateline.

Critics of the JCPOA, including Secretary of State Rex Tillerson, disagree with it in part because its relatively narrow scope -- the text of the deal focuses specifically on Iran's nuclear ambitions and is not tied to its greater moves in the region.

"President Trump has made it clear: We must take into account the totality of Iranian threats, not just Iran's nuclear capabilities," Tillerson said, referring to what Washington sees as destabilizing activity in Syria and support for terrorist groups.

In recent days, top Iranian officials have become more vocal about pushing back, saying Iran has never violated the deal and that the U.S. is trying to unfairly undermine it.

"The Iranian people proved the world that they have never lied, and won't do so, and always are complied with their commitments," Iranian President Hassan Rouhani said Sunday, according to Iran's official Islamic Republic News Agency.

In a message from Trump today, read by Energy Secretary Rick Perry, the president reportedly called on the IAEA to be tougher in its monitoring of the deal and said the U.S. "will not accept a weakly enforced or inadequately monitored deal."

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